Method for making cores of magnetic material for electromagnetic coils



March 4, 1947.

M. C. GAUTHIER 2,416,989 METHOD FOR MAKING CORES OF MAGNETIC MATERIAL FOR ELECTROMAGNETIC COILS Original Filed Nov. 6, 1943 m F/G/ lNVENTOR M. C. GAUTH/El? A TTZPNEY Patented Mar. 4, 1947 METHOD FOR MAKING CORES NETIC MATERIAL FOR NETIC COiLS OF MAG- ELECTROMAG- Marcel C. Gauthier, Montclair, N. J assignor to Western Electric Company, Incorporated, New York, N. Y., corporation of New York Original applicati n November 6, 1943, Serial No. 509,334. Divided and this application August 25, 1944, Serial No. 551,240

2 Claims.

This invention relates to a method for making cores of magnetic material for electr magnetic coils and more particularly to a method for making laminated coils of magnetic alloys whose high magnetic characteristics produced by heat treatment and annealing are damaged by even a slight measure of cold working after annealing.

A very useful type of magnetic core fo e ctromagnetic coils is made by winding a flat strip or ribbon of suitable magnetic alloy fiatwise on itself in successive coils about a suitably shaped arbor until the desired cross-sectiona area is attained. Such a core then is an unbroken annulus or ring, which will be circular, square, oblong or have some other polygonal form accord ing to the shape of the arbor used. The magnetic path of such a core is continuous around the core and is laminated transversely, both desirable characteristics. It the core is to be circular, elliptical, or otherwise without flattened straight portions, there may be but little difi'iculty in making it generally as described. However, if as may frequently be the case, the core is to have the form of a square or oblong with rounded corners and straight sides it may be difficult to achieve satisfactorily straight sides and still retain or develop the magnetic characteristics of the material satisfactorily. This is particularly so when the ribbon from which the core is wound is made of one of the various high nickel alloys of iron generally called Permalloy. When such a ribbon is Wound on a rectangular mandrel or former, the successive turns will lie snugly on each other around the corners of the mandrel, but will tend, because of the elasticity of the material of the ribbon, to arch away from the mandrel along its straight faces.

An object of the present invention is to provide a method for mak ng wound ribbon cores of magnetic material'in annular shape with straight portions in which the straight portions will consist of closely apposed individually straight portions of the ribbon having no inherent tendency to curve.

With the above and other objects in view the invention may be emborLed in a method of making such cores comprising steps of winding 2. flat ribbon upon itself in successive turns on a mandrel having one or more fiat faces, pressing the wound ribbon against the flat faces of the mandrel under pressure sufficiently severe to flatten against the fiat faces of the mandrel all portions of the ribbon passing thereover, and heat treating and annealing the mandrel and ribbon together while maintaining the pressure on the 2 ribbon against the mandrel to remove all internal stresses from the flat ribbon portions and to bring the ribbon material to maximum magnetic permeability.

Other objects and features of the invention will appear from the following detailed description of one embodiment thereof taken in connection with the accompanying drawings in which the same reference numerals are applied to identical parts ir the several figures and in which Fig, 1 is a view in front elevation with parts broken away of a device constructed in accordance with the invention;

Fig. 2 is a section on the line 2-2 of Fig. 1, and

Fig. 3 is a detached view of a mandrel and magnetic ribbon wound thereon before being compressed in the device of Fig. 1.

In making one form of laminar magnetic core in accordance with the invention, a fiat ribbon ill of suitable magnetic material, e. g., Permalloy, is wound, as shown in Fig. 3, flatwise in successive turns on a mandrel H of suitable heat resisting material, e. g., a ceramic such as porcelain or Lavite. In this instance the mandrel is a rectangular oblong with rounded corners and with straight sides between the rounded corners. A turn or two of paper tape l2 are wound on the mandrel and the metal ribbon I0 is wound over this. When the ribbon is wound on the mandrel, since the alloy of the ribbon has more or less elastic stiifness, the turns will spring in some such fashion as is indicated in Fig. 3, departing more and more as the winding continues from the desired flat sided form.

The core as wound and shown in Fig. 3 is then laid, in the position shown in Fig. 1, on the lower crossbar M of a rectangular, rigid, metal frame, generally indicated at 18, standing on the bed [9 of a press whose ram 20 is shown at the top of Fig. 1, but is not shown in Fig. 2. A pillow block 2| is inserted between one end of the coil (the right end in Fig. 1) and the adjacent upright member of the frame (upright H in Fig. 1). A pillow block 22 is laid on the upper side of the wound core. The pressure tool generally indicated at 24 is placed in position. This tool has two vertical parallel driving pins 25 and 26 which pass through corresponding bores 21 and 28 in the upper crossbar 15 of the frame l8, the homes being materially larger than the pins. The pin 25 is held in a lower crosshead member 29 in a closefitting bore 30 counterbored at 3| to receive and retain the head of the pin. The pin 26 is loosely supported and retained in an oversized bore 32 having an oversized counterbore 33 for the head of the pin. An upper crosshead member 34 is secured on the lower crosshead member 29 by screws 35, 35. The fiat heads of the pins 25 and 26 bear flatly against the member 34 and are held in place thereby, the pin 25 rigidly and the 131x125 with some freedom to shift laterally if the spacing of the bores 21 and 28 varies slightly from frame to frame. The ram 20 of the press is then brought down on the tool 24 and acts through the pillow block 22 to squeeze the upper and lower sides of the wound core flat as shown in Fig. 1. One or more suitable spacing blocks 36 and shims 31 are then inserted between the pillow block 2'2 and the crossbar I5. The ram 20 is raised and the tool 24 removed, the block 22 being retained in position to hold the sides of the core flat by the block or blocks 36 and shim or shims 31..

The frame I8 is then turned 90 clockwise to stand on the upright I'I, now resting horizontally on the press bed I9. The tool 24 is replaced under the ram with its pins 25 and 26 passing respectively through corresponding bores I21 and I28 in the bar I6 of the frame and pressing against a pillow block 23 placed against what was the left end and is now the top end of the core. The ram 20 is then brought down as before and the ends of the core squeezed fiat between the block 23 and the block 2 I. One or more spacing blocks I36 and shims I31, I31 are inserted between the block 23 and the frame bar IS. The ram is retired, and the tool 24 removed. The core is then held locked in the frame with its sides and ends flat as shown in Fig, 1.

The frame with the core thus locked in place and in proper shape within it is then heat treated as necessary to develop the desired magnetic characteristics of the metal of the core. For example, in the case of one kind of Permalloy ribbon, the treatment consists in heating to about 1975 F. for about an hour and then cooled slowly. One result of this is to develop in the metal a very high magnetic permeability, another is to burn out and wholly remove the paper coils I2 between the mandrel II and the ribbon I thus making the mandrel easily removable from the finished core; and a third is to anneal all internal stresses in the ribbon so that the turns will remain flat and snug along the straight portions of the core. The burning away of the paper also rea 4 leases the pressures on the spacing blocks and shims, so that ordinarily, when the assembly has cooled enough to handle, the finished core and the spacer blocks and shims can be taken out of the frame with the fingers.

The apparatus herein described forms no part of the present invention, but is described and claimed in copending application Serial No. 509,334, filed November 6, 1943, by the present inventor, of which application the present application is a division.

What is claimed is:

1. The method of making a magnetic core which comprises steps of covering the winding surface of a mandrel having a flat face thereon with combustible material, winding a ribbon of magnetic metal flatwise in successive turns upon the mandrel over the combustible material thereon, exerting pressure on the portions of the turns of ribbon overlying the flat face, and heating the ribbon and mandrel together while maintaining the said pressure to a temperature suflicient to remove internal stresses from the ribbon and sufficient to destroy the combustible material and thereby render the mandrel easily separable from the annealed core and the core from the pressure exerting means.

2. The method of making a magnetic core which comprises steps of covering a supporting member with heat destructible material, putting together a metal assembly on the heat destructible material, exerting pressure of the assembly on the heat destructible material and thereby against the supporting member, and heating the whole while maintaining the said pressure to a temperature sufficient to destroy the heat destructible material and thereby render the assembly easily separable from the supporting member upon cooling.

MARCEL C. GAUTHIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,586,889 Elmen June 1, 1926 2,288,855 Steinmayer July '7, 1942 2,220,732 Sander Nov. 5, 1940 

